Thermally-operated control means



United States Patent 3,194,074 THERMALLY-OPERATED CONTROL MEAN MaynardE. Anderson and John Chapa, Birmingham, and Melvin W. Polhinghorn,Livonia, Mich, assignors to American Radiator 8: Standard Sanitary(Iorporatiou, New York, N.Y., a corporation of Delaware Filed Nov. 16,196i, Ser. No. 152,723 8 Claims. (53*. 73363) This invention relates tothermally-operated control devices, as for example electric switches andfluid valves. The invention, among its features, includes the use of arecently developed crystalline material comprised of manganese, chromiumand antimony, said material having the unusual property of having littleor no dimensional change in a low temperature range, but undergoing asubstantial dimensional change per unit temperature change in a highertransition temperature range. The sharp nature of the dimensional changemakes the material partic ularly advantageous as an operator forvarioustherinally actuated control devices, particularly control deviceswhich are required to have snap-action in response to small temperaturechange.

One object of the present invention is to provide improved controldevices which utilize the advantageous characteristics of theaforementioned manganese-chromium-antimony compound.

Another object of the invention is to provide a thermally actuatedcontrol device which is operated by a relatively small temperaturechange.

A further object of the invention is to provide a thermally operatedcontrol device which can easily be manufactured to operate at precisetemperatures and which will retain its manufactured operatingcharacteristics after prolonged service.

Other objects of this invention will appear from the followingdescription and appended claims, reference being had to the accompanyingdrawings forming .a part of this specification wherein like referencecharacters designate corresponding parts in the several views.

In the drawings:

FIGURE 1 is a view of one embodiment of the invention with parts thereofshown in section;

FIG. 2 is a view partly in section of a second embodiment of theinvention;

FIG. 3 is a sectional view through a third embodiment of the invention;

FIG. 4 is a sectional view taken on line 44 in FIG. 3;

FIG. 5 is a right end elevational view of the FIG. 3 embodiment; and

FIG. 6 is a sectional view through another embodiment of the invention.

Before explaining the present invention in detail, it is to beunderstood that the invention is not limited in its application to thedetails of construction and arrangement of parts illustrated in theaccompanying drawings, since the invention is capable of otherembodiments and of being practiced or carried out in various ways, Also,it is to be understood that the phraseology or terminology employedherein is for the purpose of description and not of limitation.

Referring to FIG. 1, there is shown a thermally-operated electricalswitch comprising a conventional snap action switch housing havingmounting holes 12, a tubular cylindrical guide structure 14, and aswitch-operating plunger 16 slidably disposed within the guidestructure. The .switch'housing .10 may have any suitable form of snapaction'switch blade therein, as for example a blade constructed as shownin U.S. Patent 2,669,618. -Preferab'ly the switch is made so that only arelatively small movement of plunger 16, as for example .0005 inch, isrequired to actuate the switch.

For plunger actuation purposes there is provided a thermally responsivepower means comprising a fixed tubular sleeve element 18 and a slidablecylindrical rod element 20. Element 18 may be constructed of anysuitable material which undergoes negligibledimensional change per unittemperature change, while element 20 is preferably formed of acrystalline material having the formula 'Mn Cr Sb ln where 0.025x0.20and og goos According to an article entitled Evidence for anAntiferromagnetic-Ferrimagnetic Transition in Cr-Modified Mn Sbappearing at pages 509 through 511 in Physical Review Letters, volume 4,Number 10, issued May 15, 1960, the indium in the compound actsprincipally to retend the precipitation of Mn Sb and does not otherwiseaffect the characteristics of the compound. It is therefore contemplatedthat the compound can be employed without the indium. Themanganese-chromium-antimony material is advantageous in that in certaintemperature ranges it experiences a relatively large dimensional changeper unit temperature change. The temperature range in which the largedimensional change occurs may be varied by varying the chromiumconcentration within the limits above specified.

One crystalline material within the above specified composition rangeexperiences a relatively small linear dimensional change ofapproximately .001 percent per degree until the temperature reaches atransition value of approximately C., whereupon the material thenundergoes a linear dimensional change of approximately .2 percent duringthe next five degree temperature rise. By varying the chromiumconcentration in the compound the transition point can be lowered fromthe 100 C. value. It can be seen that the material has negligible linearexpansion per unit temperature change below its transition temperaturebut has substantial linear expansion of about .04 percent per degree inits transition temperature range so that it can be advantageously usedas the material for element 20. In an actual construction whereinplunger 16 requires a movement of .0005 inch for actuation of the switchblade,-elernent 2-0 may have a length of approximately one inch, inwhich case the switch is actuated by a temperature change of one or twochange per unit temperature change since element 20 has.

sufficicut expansion properties in its transition temperature range toprovide a satisfactory net movement. Thus, operation of the controldevice of this invention depends primarily on the characteristics ofelement 20, which operation is distinct from the usual operation ofprior art devices which depended on the differential expansioncharacteristics of two telescoped elements, each having a relativelysmall thermal expansion characteristic.

In order for the FIG. 1 device to properly operate with snap action,element 18 must be adjusted on tubular guide 14 so that the highexpansion period for element 20 occurs when plunger 16 is beingactuated. Calibration may be accomplished by maintaining element 20 atthe actuation temperature, mechanically forcing sleeve 18 onto tu Ibularguide structure 14 as a press fit, and halting the press fit movementwhen plunger 16 is actuated. With this arrangement the plunger 16 willthereafter always be actuated during the period when element 20 isundergoing its sharp increasein linear dimension.

Referring now to the FIG. 2 construction, tubular ele ment 18 thereofenjoys a non-adjustable press fit on tubular guide structure 14, andscrew 22 is threaded into the enlargement 24 of element 18. Calibrationof the device may be accomplished by holding element 20 at the desiredactuation temperature and turning screw 22 until plunger 16 is operated.After calibration the FIG. 2 device operates in the same manner as theFIG. 1 device.

The embodiment of the invention shown in M68, 3, 4 and 5 comprises arigid frame 26 having two arms 23 and St). The portions of the armsadjacent their free ends are notched, asat 31, to form fulcrum areas forthe oppositely facing edges and 34 of the resilient lade As best shownin HG. 4, blade 36 is provided with an elongated cut away area 38 whichdefines two longitudinally extending blade arms 4% and 42 and two facingblade edges and 4d. Elongated arm portions ill 42 are interconnected bya raised bridge portion which, as shown in FIG. 3, engages the plunger5b of a conventional snap action switch housing 52. The raised nature ofbridge 4-8 provides a free space between blade edges and for receptionof the thermally responsive power means generally designated by numeral5 The illustrated power means comprises a sleeve-like support element 56and a rod-like thermal expansion element 2t) preferably formed of thechromium-manganese-antimony material previously specified.

The right end of element Zt'l abuts against the right end wall ofelement 5-6, and the left end of element 2% abuts against a slidableplug 58 which retained against rotary motion by means of a ltey-lilteextension to operating in a slot 62 which is formed in the enlarged endportion of element 5d. Plug 53 is of hollow construction and threadedlyaccommodates a screw 64, the left end of which is notched to havefulcrum engagement with the aforementioned edge 46 of blade 35. Members53 and together function as a slack take-up device for ensuring that theopposite extremities of power means 54 will operatively engage the bladeedges and 4d and will cause a deflection of blade 36 when element Ed isundergoing its period of high expansion.

Blade 36 is preferably formed with a slight downward bow as shown, andis installed so that its edges 32 and are spaced slightly away from theadjacent surface areas of arms 28 and 3d. As a result, any tendency ofpower means 54 to expand will cause the blade to move towar a flattenedcondition, with consequent upward movement of bridge In its PK}. 3position power means 54 is in a low temperature COI'l't'llfiBClcondition wherein blade 3-5 is bowed downwardly and plunger 56 isextended from the switch housing 52. Raising of the ambient temperaturethrough its transition temperature range causes element to undergo asubstantial linear expansion, whereupon blade 36 moves toward aflattened condition with the central bridge portion 43 of the blademoving upwardly to thus actuate plunger 59.

The FIG. 3 construction is advantageous in that a relatively smalllinear dimensional change of element 21? results in a relatively largeflexing of blade 3%; thus a switch 52 having a relatively long plungeroperating stroke can be employed. Such long stroke switches are lessexpensive than the switches required in the PEG. 1 and FIG. 2constructions wherein small plunger motions are relied on to actuate theswitch blades.

Because the dimensional change per unit temperature change for element2% has a relatively great effect on plunger 5% any undesired tolerancevariations in the axial dimension of the thermally responsive powermeans 54 or blade 36 will have a magnified error-producing tendency.However, adjustment structure 64 may be turned to properly calibrate theconstruction in spite of such manufacturing tolerance variations.

The FIG. 6 embodiment comprises a support structure having a cylindricalside wall "ill, a radial wall '72, and a tubular sleeve-like wall 74.Disposed within the support structure is a rod element 2% preferablyformed of the aforementioned manganese-chromium-antimony material. Theupper end of element engages the bottom wall portion '76 of a cup-shapedthrust element 78. The knife edge portion Ell of the thrust elementengages a curved disc 82 on an annular line of contact disposed inwardlyof the annular fulcrum line of contact 34 for the curved disc. ispreferably not importer-ate; instead it is preferably formed with radialnotches extending inwardly from its periphery so that may bettermechanically expand or breathe when it is axially actuated by rod 2b. Inoperation, thermal expansion of element 29 causes thrust element '18 topush disc 32 upwardly from its deeply bowed condition toward but notnecessarily to a flat condition (not shown).

The on tral portion of disc 32 en ages the operating movement of rodproduces a magnified movement of plunger fill. in this way a relativelysmall length of material 26 may be used to actuate the conventional snapswitch which requires approximately .005 inch of plunger stroke foractuation. FIG. 6 is semi-schematic in character, and it is contemplatedthat suitable adjustment devices (not shown) may be incorporated incommercial forms of the device to insure that element 253 will undergoits period of highest expansion when disc 82 is being operated.

Tie drawings show the invention as incorporated in therrnaliy operatedelectric switci e it is contemplated, however, that the invention incertain of its aspects can e incorporated in other thermally operatedcontrol devices such as fluid valves and electrical potentiometerdevices, this being particularly the case with respect to the use of thechrorniunvmanganese-antimony material as a thermally responsive powermeans. lt will be understood that variations in construction andarrangement may be resorted to as come within the scope of the appendedclaims.

We claim:

In combination, a thermally responsive power means, including a supportstructure having a negligible coelhcient of thermal expansion, and athermal lenient carried by said support structure; said thermal elementbeing formed of a material comprising the compound lvin Cr Sb ln wr ere9.8255935020 and Oydfli n combination thermally responsive power means,

a including a support structure having a negligible coeilicient oftherml expansion, and a thermal element carried by said upport struesre;said thermal element being formed of a material comprising the compoundMn Cr;,Sb where 0.025X0.2Q and Cyg lfii 3. The combination of claim 2wherein the thermal element comprises an eion ated rod formed of theaforementioned material, the support structure comprises a sleeve-likesupport structure su 'onnding said rod in intimate thermal engagementtherewith along a substantial portion or the rod length.

i. In combination, a thermally responsive power m ans, comprising anelongated support st" ture having a negligible dimensional ch age p unittemperature change, and an elongated rot. carried thereby; said rodbeing formed of a material which in a low temperature range has adimensional change per urlt temperat e change on the order of .fiillpercent per degree and which in a higher temperature range experiences adimensional change on the order of .04 percent per degree.

5. In combination, an elongated flexible blade having two facing edgesarra= ged so that a longitudinal force acting thereagainst is eicctiveto flex the blade in a direc- 5 compound Mn Cr Sb Where 0.025x0.20 andOyilOS.

7. The combination of claim 5 wherein the power means is adjustable inlength independently of temperature to take up potential slack betweenthe power means I and the facing edges of the blade.

8. In combination, a curved disc; support means engaging the peripheraledge of said disc to locate same for axial movement of its central area;and thermally responsive power means for operating said curved disc,includ ing a thrust element having an operating line of contact With thedisc located radially inwardly from its peripheral edge, a substantiallynon-expansihle tube rigid With the support means and disposed on theline of action of the thrust element, and a thermal expansion roddisposed Within the tube in pressure relation With the thrust element;said expansion rod being formed of a material comprising the compound MnCr Sb where 0.025 x020 and 0. .y0.05.

References Cited by the Examiner UNlTED STATES PATENTS OTHER REFERENCESSwoboda et al.: Evidence for an Antiferromagnetic-FerrimagneticTransition in Cr-Modified M11 51), Physical Review Letters, vol. 4, No.10, May 15, 1960, pages 509-511. Pages 5 09-511 relied on.

ISAAC LISANN, Primary Examiner.

20 B. A. GELHEANY, P. K. SCHAEFER, Examiners.

0.025<X<0.20 AND 0<Y<0.05
 1. IN COMBINATION, A THERMALLY RESPONSIVEPOWER MEANS, INCLUDING A SUPPORT STRUCTURE HAVING A NEGLIGIBLECOEFFICIENT OF THERMAL EXPANSION, AND A THERMAL ELEMENT CARRIED BY SAIDSUPPORT STRUCTURE; SAID THERMAL ELEMENT BEING FORMED OF A MATERIALCOMPRISING THE COMPOUND MN(2-X)CR(X)SB(1-Y)IN(Y)